1. Field of the Invention
This invention relates to an apparatus and method useful for offshore oil spill clean-up and, more particularly, to a specialty boom and outrigger system for gathering spilled oil to be recovered by an offshore skimmer.
2. Description of the Related Art
It is an opening concern for parties involved in offshore petroleum exploration, production and transportation to minimize danger to human and marine life and damage to the ocean and beach environment. Proper planning and execution of oil spill control is essential to the accomplishment of that goal. Effective containment and recovery of spilled oil allows damage to be minimized and limits expenses and opportunity costs of redirecting limited resources, such as equipment and manpower from their primary purpose.
Various types of equipment have been used to contain or gather spilled oil, including suction nozzles, weir skimmers, sorbents and other special devices designed for this purpose. The use of suction nozzles is effective at recovering thick layers of oil, but is limited by waves. When used on thin or patched oil slicks, suction nozzles collect a disproportionately large amount of water, requiring huge storage and separation facilities. Sorbents and gelling agents are difficult to distribute and recover when used over a large area. Large spills require significant amounts of sorbents, the handling and disposal of which is extremely costly.
A skimmer device includes an engine and suction pump that is propelled over the water and sucks or paddles oil into a tank. The skimmer can be mounted on a skiff or small boat. The boat is maneuvered to where the oil has been corralled with the use of an oil spill boom so that the skimmer takes the oil off the top of the water like a vacuum cleaner and pumps it into a tank. Weir skimmers allow the surface layer of oil to flow by gravity into a container. They are effective on thick layers of oil when waves and the current are small. If the oil layer is thin or the waves are large, weir skimmers, however, collect water in large quantities.
Presently, offshore skimming units require a means of carrying the skimmer, means of corralling the oil to the skimmer and means of storing the skimmed fluids. Typically, one work boat carries the skimmer and one or two vessels corral the spilled oil by dragging a long length of approximately 300' of regular oil containment boom between them or attached to the skimmer vessel. The use of conventional oil containment booms for corralling spilled oil presents several problems. First, maneuvering is difficult when a second boat is required to control the boom. At speeds of more than one knot, skimmed fluids pass under the boom, making corralling ineffective. Because conventional booms typically have very little freeboard, waves typically splash over the top of the boom carrying the oil with them. In addition, it is frequently necessary to utilize a large vessel, such as a 120 ft. workboat, to withstand rough seas. The need for workboats is costly both in terms of expense and opportunity cost. Finally, large expensive outrigger-tank combinations are available for use in conjunction with this method of corralling but are cost prohibitive and require additional equipment in order for them to be erected on the skimmer vessel. Thus, there is a need for an oil spill recovery apparatus that is cost effective, minimizes the use of valuable resources and functions efficiently at corralling spilled oil.